Phase III, randomized, double-blind, placebo-controlled trial of oral acyclovir for localized cutaneous zoster in 3 groups of immunocompromised patients. Via objective and subjective evaluation over a course of 1 year, the hypothesis that this medication accelerates cutaneous healing, decreases acute neuritis and post-herpetic neuralgia and decreases the frequency of cutaneous and visceral dissemination will be tested.